Support with adjusting means



June 20, 1967 w. W. BIRD ETAL 3,325,887 SUPPORT WITH ADJUSTING MEANS Filed Oct. 16, 1961 ,2 Sheets-Sheet 1 INVENTORS M11548 M: 5/40 4W0 W en Y6 June 20, 1967 w, w. BIRD ETAL 3,325,887

SUPPORT WITH ADJUSTING MEANS Filed Oct. 16, 1961 2 Sheets-Sheet 2 INVENTORJ'; WQLTE'Q 7M 5020 IND w Qa up United States Patent Force Filed Get. 16, 1961, Ser. No. 145,517 2 Claims. (Cl. 29--256) This invention relates to air'supported parabolic reflectors and more particularly to a method for joining together individual panels of fabric material to produce said reflectors and an apparatus for supporting an airinflated parabolic antenna assembly such that the final contour of the resultant antenna can be controlled within close tolerances.

Air supported fabric assemblies having a parabolic contour have proved to be of value as radio energy reflectors. These reflectors are constructed by joining together individual pie-shaped panels of a flexible fabric material, such as vinyl coated fiberglass. The panels are joined together in such a manner as to form a balloon-like airinfiated structure having two symmetrically shaped parabolic half sections. One of the parabolic half sections is transparent to electromagnetic RF. energy While the other parabolic half section is coated with an energy reflective material such as vapor deposited aluminum, aluminum particles or a silver pigmented vinyl resin.

The use of flexible woven fabrics in the manufacture of structural assemblies requiring close constructional and operational tolerances has presented serious problems due to the nonuniform characteristics of the fabric material. The warp tension and elasticity of these woven fabrics varies considerably in different sections of a fabric roll and, as a result, it is extremely dilficult to produce a predetermined shape of precise construction within the contour tolerances required for antenna use.

Prior methods of construction in the field of parabolic antennas, such as sewing or cementing, proved to be inadequate in providing the necessary control over the shape of the final antenna structure. Consequently, in order to take advantage of the desirable lightweight characteristics of a woven fabric material, it is necessary that the fabric panels be joined together in a manner that will produce a smooth parabolic contour and permit close tolerance construction of the antenna assembly.

Accordingly, it is the primary object of this invention to circumvent the above described deficiencies of the prior art by providing a method and apparatus for the close tolerance construction of structural fabric assemblies having a precise predetermined shape.

Another object of this invention is to provide a method for producing an air-inflated fabric structure having a parabolic shape.

A further object of this invention is to provide an ap paratus for supporting a preassembled fabric structure such that the tension and position of this fabric can be adjusted to obtain a smooth contour of predetermined shape.

The above and still further objects, and advantages of this invention will become readily apparent upon consideration of the following detailed disclosure thereof taken in conjunction with the accompanying drawings wherein:

FIGURE 1 is a view partly in section of the apparatus of this invention showing a portion of the fixture utilized to position and tension the outer ends of the antenna panels;

FIGURE 2 is an isometric view, partly in section of the apparatus of this invention showing the fixture employed for adjusting the inner ends of the antenna panels;

FIGURE 3 is a plan view of an alternative embodiment for the individual adjustment of the tension and position of the inner end of each antenna panel;

FIGURE 4 is a schematic representation of an air supported parabolic antenna assembly; and

FIGURE 5 is a schematic representation of the apparatus of FIGURE 1 and FIGURE 3 oriented for tensioning a parabolic reflector.

In order to assemble this type of antenna structure, it is necessary to pre-tension the panels forming the parabola in order to provide elastic characteristics that are as uniform as possible. The elastic characteristics of the material under load may be taken into account in patterning the unit in order to keep the required adjustment to a minimum.

After the panels or gores are cut to size and marked for assembly, they are joined together by cementing or heat sealing using a fin-type joint of sufiicient strength to support the structure when inflated. The completed assembly is then mounted in a fixture which will support the panels in a manner similar to that of the final configuration. The fixture is so constructed that a pressure differential can be maintained across the material equal to that used for the completed antenna. Thus, the weight component and other factors causing distortion are accounted for during final adjustment. The fixture is described relative to FIGURES 1 through 3.

Referring to FIGURE 1, there is disclosed an adjusting fixture which is utilized to provide uniform support for the outer edges of a number of fabric panels which are joined together to form the paraboloid shaped half section which can be joined to a similar mating section to form an air-supported parabolic shaped antenna assembly. This fixture supports the outer edge of the panels in a manner which allows for the adjustment of the entire circumference of the paraboloid half section.

A rope I9 is inserted in the outer end of the fabric panel 12 and a slotted tube 14, fabricated from soft aluminum or other pliable material, is slipped over the roped edge in order to provide for continuous support. The tube 14 is in turn held by a tong-type adjusting clamp 16 and adjusting nut 18. The clamp 16 can be slipped along the tube 14 to any point where support or adjustment is required.

This support is spaced in such a manner that the fabric loads are distributed by the slotted tube, yet, the tube can still be shaped to provide fine contour adjustment as required. The clamp 16 is supported by means of a bracket 20 which slips over the extended flange of a circular angle frame 22 and is positioned thereon by means of a set screw 24. v

The adjustment of the inner ends of the fabric panels is accomplished by employing the adjusting fixture disclosed in FIGURE 2. This fixture comprises a tubular ring 26 attached to a circular angle frame 28 by means of adjusting screws 30. The inner ends of the fabric panels 32 are cemented or otherwise secured to the tubular ring 26 and are adjusted and tensioned by means of the adjustment screws 30.

When adjustment of the fabric panels is completed, the final contour of the panels is fixed by cementing a ring 34 to the panel ends. The adjustment ends are then trimmed off and a closure sheet is sealed across the opening to complete the antenna surface.

FIGURE 3 discloses an alternative embodiment for securing adjustment of the inner ends of the panels. The panel ends 46 are attached to brackets 47 on adjusting screws 48 by means of cementing or clamping. The adjustment screws 48 are in turn attached to a circular framework Stl. By utilizing the adjustment screws 48, the panels can be individually tensioned during the con- 3 touring process and maintained in their proper position until the seams have been fixed by final taping.

The holding fixture comprises the support of FIGURE 1, and either of the supports of FIGURES 2 or 3 which are fixed relative to one another on the axis of the parabola in accordance with the parameters of the desired parabolic shape. Any mount of conventional construction which fixes the supports may be utilized. The jigs of FIG- URES 1 and 3 are shown in FIGURE 5 mounted on the axis of the parabola to accord with the parameters of the desired parabolic shape.

The material to be utilized for the reflective half section of the antenna is coated; however, an oppositely disposed half section, transparent to RF. energy, is .positioned on supports identical to that previously described. The half sections are placed in contact such that the outer edges may be sealed such that a balloon-like structure results. An inflated tube or rim 42 (FIGURE 4) is secured to and supports the structure at the joining points of the oppositely disposed half sections.

Although the parabolic half section which is transparent to R.F. energy is shown in FIGURE 4 as being identical to the reflective half section, it need not be supported in the same manner nor have an identical contour to that of the reflective half section since the final shape of the non-reflective portion is not critical.

A small compressor is attached to the unit and the tube or rim at convenient places and the antenna is inflated to a pressure of at least p.s.i. A pressure differential of as little as .02 p.s.i. is sufficient for satisfactory operation. At this point, although there might be a small amount of leakage due to the fact that the rim and end portions are not yet sealed, the device will inflate. Individual adjustment of the tension and position of each panel is effected while the antenna is inflated. When the adjustment is completed, the final position of the antenna is fixed by cementing the ring 34 to the antenna, trimming off the adjustment ends and securing the outer ends to the inflated tube or rim 42 (FIGURE 4).

Finer adjustments may be achieved by utilizing a template prior to the application of a closure sheet across the central opening of the parabolic reflector. This template would be placed against the inflated fabric on the axis of the parabola, and minor adjustments may be made by opening the seams at the joints of the individual panels by means of a solvent or the application of a concentrated pressure across the jointed seams. In order to permanently fix the position of the jointed seams after adjustment, a vinyl coated fiberglass tape is cemented across the fin-joint seam and firmly rolled; thus, excessive overpressurization or handling problems will not cause a change in contour. A zipper joint may be provided on the antenna at any convenient position in order to allow workmen to enter and to allow for the removal of the template and supports.

The antenna assembly shown in FIGURE 4 has the paraboloid half section 36 coated with, for example,

vaporized aluminum while the other paraboloid half section 38 remains transparent to energy. A feed horn 40 in conjunction with the support tube 42 and a suitable supporting framework 44 complete an antenna assembly which is capable of superior performance over conventional antennas, and at the same time is dimensionally stable.

It will be understood that while the method and apparatus disclosed herein illustrate a preferred form of the invention, modifications can be made by those skilled in the art without departing from the spirit and scope thereof and all such modifications as fall within the scope of these appended claims is intended to be included herein.

We claim:

1. A jig for supporting, prior to final contouring, a half section of an inflatable object of flexible material having a surface of revolution wherein cross-sections perpendicular to the axis of said surface of revolution form circles, comprising a pair of toroidal supports having coincident central axes, said toroidal supports being spaced along said axis, the size of said toroids corresponding to the shape of said half section at the position of each of said supports along the axis of said surface of revolution, and adjustable means on each of said toroidal supports for clamping the material forming said half section and adapted for continuously adjusting the tension thereof.

2. In combination, a half section of an inflatable object of flexible material having a surface of revolution wherein cross-sections perpendicular to the axis of said surface of revolution form circles, and a jig for supporting said inflatable object prior to final contouring, said jig comprising a pair of toroidal supports having coincident central axes, said toroidal supports being spaced along said axis, the size of said toroids corresponding to the shape of said half section at the position of each of said supports along the axis of said surface of revolution, and adjustable means on each of said toroidal supports for clamping the material forming said half section and adapted for continuously adjusting the tension thereof.

References Cited UNITED STATl-fi PATENTS 2,342,025 2/ 1944 Watter. 3,024,525 3/1962 Wisberger 294-Z1 FOREIGN PATENTS 989,286 5/1951 France. 746,300 3/ 1956 Great Britain. 838,250 6/1960 Great Britain.

WILLIAM FELDMAN, Primary Examiner.

ARTHUR M. HORTON, BENJAMIN A. BORCHELT,

MYRON C. KRUSE, Examiners.

S. W. ENGLE, Assistant Examiner. 

1. A JIG FOR SUPPORTING PRIOR TO FINAL CONTOURING, A HALF SECTION OF AN INFLATABLE OBJECT OF FLEXIBLE MATERIAL HAVING A SURFACE OF REVOLUTION WHEREIN CROSS-SECTIONS PERPENDICULAR TO THE AXIS OF SAID SURFACE OF REVOLUTION FORM CIRCLES, COMPRISING A PAIR OF TOROIDAL SUPPORTS HAVING COINCIDENT CENTRAL AXES, SAID TOROIDAL SUPPORTS BEING SPACED ALONG SAID AXIS, THE SIZE OF SAID TOROIDS CORRESPONDING TO THE SHAPE OF SAID HALF SECTION AT THE POSITION OF EACH OF SAID SUPPORTS ALONG THE AXIS OF SAID SURFACE OF REVOLU- 